I understand that Ed Norton wanted a bigger paycheck, and refused to reprise his role as the Hulk. That was very disappointing for me, but I moved on. But why did they choose Mark Ruffalo as Bruce Banner/Hulk? I think his performance wasn't bad, but it just didn't feel like the character at all to me.

He signed on for 6 more films, so it seems like he is here to stay. Why did they choose Mark Ruffalo as the Hulk?